Data on daily climatic conditions as reported from approximately 300 weather stations will be obtained from the National Climatic Center, and linked to daily mortality data for the period 1972 through 1977. An age-specific analysis of average daily mortality at various levels of climatic variables will be performed in order to ascertain relationships between age and climatic conditions. Climatic variables will include temperature, relative humidity, rapid changes in temperature, departures from normal temperatures, and sustained heat waves and cold fronts. Levels at which hypothermia and hyperthermia are more likely will be investigated in greater detail. Concomitant information on socioeconomic status and geographic location of the cases will also be considered.